Q: Fuses and circuit breakers seem the same to me. What is the difference between these?

A: Fuses and circuit breakers are the same in their purpose of protecting an overloaded electrical circuit by interrupting the continuity, or flow of electricity. Overloaded electrical circuits may cause damage to the electrical equipment, or in more serious cases, cause a fire. The difference begins at how they interrupt the flow of electricity. A fuse is made up of a piece of metal that melts when an electrical circuit is overloaded; thus interrupting continuity. Most common types use a metal wire or filament that is enclosed in a glass or ceramic and metal housing. A circuit breaker has an internal switch mechanism that is tripped when there's a surge of electricity. The internal switch mechansim typically uses an electromagnet (or solenoid) or a bimetal strip. Another use of the circuit breaker is a "ground fault circuit interrupter", or GFCI. This type of circuit breaker prevents electrical shock instead of overheating. It works by breaking the circuit in an outlet if the current becomes unbalanced, and can be reset by the push of a button.

A fuse needs to be replaced; a circuit breaker can simply be reset. A fuse is less expensive than a circuit breaker to install or repair. The metal wire or filament inside a fuse typically melts quickly, so any power surge is quickly stopped. A circuit breaker usually does not react as quick as a fuse. It is possible that the electronics connected to a circuit breaker could be damaged by excess electricity that still passes through to the circuit during the delay. It is also more sensitive to vibration and movement which can cause a trip for unrelated reasons. A fuse and a circuit breaker are not interchangeable in all applications. For example, a fuse cannot be used in place of a GFCI.

More information regarding fuses:The most general purpose fuses are the normal fast-blow fuses which reacts very quickly to interrupt continuity. The "time delay" fuse, "anti-surge" fuse, or "slow-blow" fuse, are designed to allow above rated current of the fuse to flow for a short period of time without the fuse blowing. These types of fuses are used on electrical equipment such as AC motors. Motors can draw a larger than rated current (inrush current) for up to a few seconds while ramping up to speed, then it drops to the rated current once the motor is at its rated speed. If you use a fast-blow fuse with an AC motor that is rated for the AC motor's rated current, then the fuse would blow.